Smartphone-based conditional access system

ABSTRACT

Techniques for a smartphone-based conditional access (CA) system are described. In some embodiments, a headend in the CA system obtains a security profile associated with a pair of receiving devices used by a user, e.g., a first device (e.g., a smartphone) and a second device (e.g., a set-top-box or a TV). The headend dynamically regulates user access to requested media content during each entitlement period by assigning and distributing separate keys to the first and second device based on the security profile. The headend also uses the distributed keys to protect the media content before broadcasting. On the receiving end, one receiving device receives the media content and determines whether it is decryptable by the device. If decryptable, the receiving device (e.g., the set-top-box/TV) decrypts the media content using the keys assigned by the headend. Otherwise, the receiving device forwards the media content to the pairing device for decryption.

TECHNICAL FIELD

The present disclosure relates generally to conditional access to mediacontent from an end-user device.

BACKGROUND

Conditional access (CA) systems are exposed to various attacks, such ascloning, CA service manipulation, entitlement manipulation, key sharing,and content sharing. In order to reduce these attacks, some CA systemsrely on security enhanced set-top-box (STB) chips as security anchors.However, such hardware-based solutions drive up the cost and create asingle point of failure. Some solutions attempt to enhance security byapplying watermarking. Such software-based solutions have limitations.For instance, downstream support cannot be relied upon in headend-basedwatermarking, e.g., content detection in non-unicast systems can take along time. In another example, since client-based watermarking relies onthe device security, it is expensive to perform watermarking in the STB.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present disclosure can be understood by those of ordinaryskill in the art, a more detailed description may be had by reference toaspects of some illustrative embodiments, some of which are shown in theaccompanying drawings.

FIG. 1 is a block diagram of an exemplary conditional access (CA) systemin accordance with some embodiments;

FIG. 2A is a block diagram of an exemplary headend system for secure keyassignment and distribution in accordance with some embodiments;

FIG. 2B is a block diagram of an exemplary headend system for securecontent delivery in accordance with some embodiments;

FIG. 3 is a block diagram illustrating media content decryption in asmartphone-based CA system in accordance with some embodiments;

FIGS. 4A-4D are block diagrams illustrating dynamic key and contentdelivery in smartphone-based CA systems in accordance with someembodiments;

FIG. 5 is a flowchart illustrating a method for service key assignmentand distribution in a smartphone-based CA system in accordance with someembodiments; and

FIG. 6 is a flowchart illustrating a method for secure content deliveryin a smartphone-based CA system in accordance with some embodiments.

In accordance with common practice the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may not depict all of the componentsof a given system, method or device. Finally, like reference numeralsmay be used to denote like features throughout the specification andfigures.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Numerous details are described in order to provide a thoroughunderstanding of the example embodiments shown in the drawings. However,the drawings merely show some example aspects of the present disclosureand are therefore not to be considered limiting. Those of ordinary skillin the art will appreciate that other effective aspects and/or variantsdo not include all of the specific details described herein. Moreover,well-known systems, methods, components, devices and circuits have notbeen described in exhaustive detail so as not to obscure more pertinentaspects of the example embodiments described herein.

Overview

Techniques for using a smartphone, or a similar end-user device, as abuilding block in a security enhanced conditional access (CA) system aredescribed herein.

Smartphones are common end-user devices. Typically, smartphones havemore capable resources (e.g., CPUs and/or two-way transport paths) thanset-top-boxes (STBs) and are more difficult to clone. Variousembodiments disclosed herein use smartphones as a building block in asecurity enhanced CA system.

In accordance with various embodiments, a method is performed at aheadend. The method includes obtaining a security profile associatedwith a first device, a second device paired with the first device, and auser. The method further includes locating a first device key for thefirst device and a second device key for the second device. The methodadditionally includes regulating user access to a channel during anentitlement period, which further includes determining a first securityranking of the first device and a second security ranking of the seconddevice based on the security profile, and assigning a first subset ofservice keys to be encrypted with the first device key and a secondsubset of service keys to be encrypted with the second device key basedon the first security ranking and the second security ranking. Themethod also includes transmitting the first subset of service keys tothe first device and the second subset of service keys to the seconddevice.

In accordance with various embodiments, a method is performed at aheadend. The method includes scrambling media content associated with achannel during an entitlement period, which further includes encryptingthe media content using at least one control word to generate encryptedmedia content, and selectively encrypting the at least one control wordwith a service key from a first subset of service keys assigned to afirst device or a second subset of service keys assigned to a seconddevice paired with the first device in order to generate at least oneencrypted control word. The method also includes transmitting the atleast one crypted control word along with the encrypted media content toat least one of the first device or the second device.

EXAMPLE EMBODIMENTS

As described above, many conditional access (CA) systems rely onset-top-boxes (STBs) for security. FIG. 1 illustrates a block diagram ofan exemplary CA system 100. The exemplary CA system 100 includes aserver side and a client side, as indicated by the dotted line. Forexample, the server side can include a headend 110, and the client sidecan include a subscriber device 160, such as an STB. In someembodiments, the headend 110 includes a device key generator 112, whichgenerates and delivers on demand unique device key(s) 114 to thesubscriber device 160. Once delivered, the subscriber device 160 storesthe received device key(s) 114 in an internal or external storage 162.In some embodiments, the subscriber device 160 includes a device key inthe hardware and/or firmware of the subscriber device 160. In suchembodiments, as will be described below, the headend 110 obtains thedevice key from the client side, e.g., during registration and/orpairing.

In some embodiments, the headend 110 also includes a service keygenerator 122 and an entitlement management message (EMM) generator 124.Transmission of EMMs 128 is generally in response to a request from thesubscriber 160 to a service provider. Further, at the request of theservice provider, the service key generator 122 generates service keys126 and provides the service keys 126 to the EMM generator 124. In orderto generate the EMMs 128, the EMM generator 124 obtains subscriber data,including at least one entitlement 118 for the subscriber (e.g., paymentfor a particular channel), from an internal or external storage 116 andcombines with the service keys 126 to form EMMs 128. An EMM 128typically includes fields such as the entitlement 118 for thesubscriber, the service keys 126 encrypted with the device key(s) 114,and/or a data integrity check field, among others.

In some embodiments, the headend 110 further includes a control word(CW) generator 132, a scrambler 134, and an entitlement control message(ECM) generator 136. The control word generator 132 generates controlwords 138 and provides the control words 138 to the scrambler 134. Thescrambler 134 obtains unencrypted media content 142 from an internal orexternal media content repository 143 and generates encrypted mediacontent 146 by encrypting the media content 142 with the control words138. For further protection, the ECM generator 136 encrypts the controlword 138 using the service keys 126 provided by the service keygenerator 122. The encrypted control words are then included in the ECMs144 to be transmitted together with the encrypted media content 146. Asused herein, the terms “scramble” and “encrypt” are usedinterchangeably, so are the terms “scrambler” and “encryptor” in someembodiments.

On the client side, in some embodiments, the subscriber device 160includes an EMM decoder 166, an ECM decoder 172, and a descrambler 176in addition to the internal or external storage 162. In someembodiments, once the subscriber device 160 receives the encrypted mediacontent 146, the descrambler 176 decrypts the encrypted media content146 in preparation for rendering. In order to decrypt the media content146, in some embodiments, the EMM decoder 166 obtains the device key 164from the storage 162 and applies the device key 164 to the EMMs 128 inorder to derive an entitlement 168 for the subscriber and the decryptedservice key 169. The EMM decoder 166 further provides the entitlement168 and the decrypted service key 169 to the ECM decoder 172. The ECMdecoder 172 then applies the decrypted service key 169 to the ECMs 144to derive a decrypted control word 174. The decrypted control word 174is then used by the descrambler 176 to decrypt the encrypted mediacontent 146. As used herein, the terms “descramble” and “decrypt” areused interchangeably, so are the terms “descrambler” and “decryptor” insome embodiments.

In some embodiments, in the key-based CA system 100, the key in eachlevel is encrypted or decrypted with the key of the previous level. Forexample, the device key(s) 114 are used for encrypting the service keys126 in the headend 110 and for decrypting the service keys 169 on thesubscriber device 160. In some embodiments, the keys of the previouslevel are used for generating keys and/or decryption in other levels.For example, the device key(s) 114 are used as a seed for generating theservice keys 126 and for deriving the service key 169. Further, in someembodiments, one key can be generated as a function of multiple seeds(or keys) and vice-versa.

As shown in FIG. 1, the CA system 100 is exposed to various attacks. Forexample, attempting to view content that one has not paid for, a usermay use an illegitimate device to duplicate the uniqueness of thesubscriber device 160 for key and/or content sharing. In anotherexample, a subscriber who purchased one service (e.g., service A) buthas not paid for another service (e.g., service B) may attempt tomanipulate the entitlement for service A (e.g., in the EMMs 128) inorder to gain access to service B. In yet another example, a user maymodify the entitlement information in the EMMs 128 to prolong theservice after the subscription expiration date. Typical off-the-shelfSTBs have limited hardware and software resources to provide strongprotection of the encrypted media content 146, the ECMs 144, the EMMs128, and/or the device keys 114. As such, a CA system that merely relieson such STBs as security anchors is vulnerable to the above-mentionedattacks.

Smartphones (and other end-user devices, such as tablets, wearabledevices, computers, and/or portable multifunction devices, etc.) arebecoming increasingly common and affordable around the globe. Typically,a smartphone is paired with its human owner and capable of having atwo-way communication with a remote server. Further, in near range, thesmartphone is capable of establish a secure two-way communicationchannel with another device, e.g., via Wi-Fi and/or Bluetooth. Inaddition, relative to off-the-shelf STBs, smartphones have more capableresources (e.g., stronger CPUs) and are more difficult to clone.Accordingly, the smartphone-based CA system disclosed herein inaccordance with embodiments leverages the above-mentioned properties ofsmartphone (e.g., affordability, communication capability, processingcapability, and/or security) and uses the smartphone as a building blockfor security enhancement.

FIG. 2A illustrates an exemplary smartphone-based CA system 200A forsecure key assignment and distribution in accordance with someembodiments. The CA system 200A includes a server side and a client sideas indicated by the dotted line. In some embodiments, the server sideincludes a headend 210 for transmitting media content, and the clientside includes multiple receiving devices used by a subscriber 260 (or auser 260), e.g., a smartphone 270 and an STB/TV 280. In thesmartphone-based CA system 200A, the smartphone 270 and the STB/TV 280are paired, so that the smartphone 270 becomes a building block of theCA system 200A. In some embodiments, the headend 210 includes a receiver220 for receiving information from the smartphone 270, a storage 222 forstoring security profiles generated based on the information receivedfrom the receiver 220, a device key generator 230 for locating and/ordelivering device keys to receiving devices used by the subscriber 260,a controller 240, and a transmitter 250 for key distribution.

In some embodiments, applications are installed on both the STB/TV 280and the smartphone 270. When the subscriber 260 registers and creates auser account with the service provider, e.g., via the application on thesmartphone 270, the profile of the smartphone 270 along with a userprofile is transmitted from the smartphone 270 to the headend 210, e.g.,via a transceiver 274 of the smartphone and through the receiver 220. Insome embodiments, the profile of the smartphone 270 includes, but notlimited to, the hardware, software, and/or firmware profile of thesmartphone 270. Further, in some embodiments, the STB/TV 280 displays(e.g., on a display of the STB and/or the TV) an identifier and otherinformation of the STB/TV 280 (e.g., the hardware, software, and/orfirmware profile of the STB/TV 280).

In some embodiments, when the smartphone 270 used by the subscriber 260is within a threshold distance from the STB/TV 280, the smartphone 270obtains the displayed information, e.g., by scanning a QR code displayedon the STB/TV 280 in order to establish the pairing. In someembodiments, through one or more transceivers 274 of the smartphone 270(e.g., WiFi and/or Bluetooth) and one or more transceivers 284 of theSTB/TV 280 (e.g., WiFi and/or Bluetooth), the smartphone 270 and theSTB/TV 280 exchange information and establish a secure near-rangecommunication channel Once the smartphone 270 and the STB/TV 280 arepaired, the smartphone 270 sends the information of the STB/TV 280 alongwith the information exchanged with the STB/TV 280 to the headend 210,e.g., via the transceiver 274 and through the receiver 220. The headend210 in turn stores the received information along with the informationof the smartphone 270 and/or the user profile of the subscriber 260received during registration in an internal or external storage 222 as asecurity profile for the subscriber 260. In some embodiments, thesecurity profile for the subscriber 260 changes over time. For example,in case of a breach of a particular phone model, the headend 210 (e.g.,the controller 240) updates security profiles stored in the storage 222involving the particular phone model. Accordingly, in case the securityprofile for the subscriber 260 indicates that the subscriber 260 usesthe particular phone model in the smartphone-based CA system 200A, theupdates affect the security profile for the subscriber 260, e.g.,indicating in the profile of the smartphone 270 that the smartphone 270is less secure.

In some embodiments, based on the security profiles, the device keygenerator 230 generates device key suites. In some embodiments, thedevice key suites include at least one unique device key for thesmartphone 270, denoted as K_(PHONE), and another unique device key forthe STB/TV 280 (different from the device key for the smartphone 270),denoted as K_(STB). Once generated, the device keys are securelydelivered to the smartphone 270 and the STB/TV 280 respectively, e.g.,through the one or more transmitters 250 of the headend 210, the one ormore transceivers 274 of the smartphone 270, the one or moretransceivers 284 and/or the receiver 288 of the STB/TV 280. Uponreceiving the respective device key, the smartphone 270 stores K_(PHONE)in a secure storage 276 associated with the smartphone 270 and theSTB/TV 280 stores K_(STB) in a secure storage 286 associated with theSTB/TV 280. In some embodiments, K_(PHONE) is included in the hardwareand/or firmware of the smartphone 270, e.g., burning the key to thedevice in the factory. Likewise, K_(STB) is included in the hardwareand/or firmware of the STB/TV 280. In such embodiments, the headend 210locates K_(PHONE) and K_(STB) from the receiving devices duringregistration and/or pairing, e.g., the device key generator 230 obtainsthe device keys from the information received from the smartphone 270and/or from the security profiles stored in the storage 222.

In some embodiments, for a channel C in an epoch E, the controller 240obtains service keys, denoted as {SK_(C,E) ¹, . . . SK_(C,E) ^(S)},e.g., from the service key generator 122 (FIG. 1). Based on the securityprofiles stored in the storage 222, the controller 240 determinessecurity rankings of the smartphone 270 and the STB/TV 280. Further,based on the security rankings, for the epoch E and for the channel C towhich the subscriber 260 is entitled, the controller 240 decides howmany service keys would be encrypted with K_(PHONE) and how many servicekeys would be encrypted with K_(STB) and encrypts the service keys{SK_(C,E) ¹, . . . SK_(C,E) ^(S)}, accordingly.

In some embodiments, instead of determining separate security rankings,e.g., one for the smartphone 270 and the other for the STB/TV 280, thecontroller 240 calculates one security ranking for a tuple associatedwith the receiving devices, e.g., <STB ID, smartphone ID, communicationtype between the smartphone and the STB>. In some embodiments, thecontroller determines the combined security ranking during the pairingand updates the combined security ranking when at least one of theprofile of the smartphone 270 or the profile of the STB/TV 280 changes.For example, in accordance with a newly discovered security flaw in theSTB/TV 280, the controller 240 lowers the combined security ranking forthe combination of the smartphone 270 and the STB/TV 280. In someembodiments, as will be described below with reference to FIG. 3, thecontroller 240 uses the combined security ranking for determiningwhether the receiving devices are secure enough to view the type ofrequested media content.

In some embodiments, in the case that a service key is encrypted withK_(PHONE), the controller 240 directs the transmitter 250 to transmitthe encrypted service key SK_(C,E) ^(i) to the smartphone 270. As usedherein, the encrypted service key(s) that are transmitted to thesmartphone 270 are denoted as SK_(PHONE). On the other hand, in the casethat a service key is encrypted with K_(STB), the headend system 210transmits the encrypted service key SK_(C,E) ^(i) to the STB/TV 280. Asused herein, the encrypted service key(s) that are transmitted to theSTB/TV 280 are denoted as SK_(STB). As will be described below, theencrypted service keys will then be used by the respective receivingdevice to decrypt the encrypted media content. In some embodiments, asdescribed above with reference to FIG. 1, the encrypted service keys aretransmitted in the EMMs 128 along with the entitlements for thesubscriber 260. Upon entitlement renewal, the headend repeats theservice key assignment and distribution process described herein.

On the receiving end, a controller 272 of the smartphone 270 uses thedevice key and the service key(s) received from the headend 210 (e.g.,K_(PHONE) and SK_(PHONE)) to perform the decryption, such as performingthe functions by the descrambler 176, the ECM decoder 172, and the EMMdecoder 166 in FIG. 1. Likewise, a controller 282 of the STB/TV 280 usesthe device key and the service key(s) received from the headend 210(e.g., K_(STB) and SK_(STB)) to perform the decryption, such asperforming the functions by the descrambler 176, the ECM decoder 172,and the EMM decoder 166 in FIG. 1. Further, as will be described belowwith reference to FIG. 3, the controllers 272 and 282 perform additionalfunctions for security enhancement.

FIG. 2B illustrates an exemplary smartphone-based CA system 200B forsecure content delivery in accordance with some embodiments. In someembodiments, the exemplary smartphone-based CA system 200B uses theservice key assignment and distribution mechanism described above withreference to FIG. 2A, and uses the service keys for content protection.As a result, elements common to FIGS. 2A and 2B include common referencenumbers, and the differences are described herein for the sake ofbrevity.

In some embodiments, the controller 240 obtains unencrypted mediacontent from a media content repository 292. In order to protect themedia content, the controller 240 encrypts the media content withcontrol words (CWs). In some embodiments, the controller 240 obtainscontrol words from a control word generator 294 (e.g., the control wordgenerator 132, FIG. 1). When encrypting media content associated with achannel C and for an epoch E, the controller 240 obtains control wordsfrom the control word generator 294. Further, for a control word, e.g.,CW_(i), the controller 240 encrypts the control word with a selectedservice key, e.g., calculating ECWi=F(CW_(i), SK_(C,E) ^(l)), where F isa reversible function and typically an encryption function. In someembodiments, for each ECW_(i), there is an indicator regarding which SKis used for decrypting the respective ECW_(i). In some embodiments, thecontroller 240 directs the transmitter(s) 250 to transmit the indicatorto the subscriber 260 to facilitate the control word decryption. Itshould be noted that in some embodiments, there are n CWs in aparticular crypto period, while there are s SKs. In other words, thecontroller 240 can choose to use some of the service keys per cryptoperiod. As such, the index of the CW and the index of the SK may bedifferent, e.g., i is different from 1. As used herein, an “epoch”refers to the length of the minimal entitlement period, e.g., 30 to 60days or shorter. Thus, the terms “epoch” and “entitlement period” areused interchangeably in some embodiments. Further as used herein, a“crypto period” refers to the time span during which a specificcryptographic key is authorized for use. For example, in every cryptoperiod, the control word is changed.

The controller 240 then causes the transmitter 250 to transmit theencrypted control word, e.g., broadcasting the encrypted control wordECWi to be received by the STB/TV 280. Further, for every media contentpacket, the controller 240 chooses a control word, e.g., choosing CWj,and encrypts the media content packet with CWj before causing thetransmitter 250 to transmit the encrypted media content packet to one ofthe receiving devices, e.g., broadcasting the encrypted media contentalong with the encrypted control word. In some embodiments, for eachencrypted media content packet, there is an indicator regarding which CWis used for decrypting the respective packet. In some embodiments, thecontroller 240 directs the transmitter(s) 250 to transmit the indicatorto the subscriber 260 to facilitate the media content decryption.

As described above with reference to FIG. 2A, based on the securityrankings, in some embodiments, the headend 210 distributes a subset ofencrypted service keys to the smartphone 270 and another subset ofencrypted service keys (different from the subset to the smartphone 270)to the STB/TV 280. As such, a subset of encrypted control words would bedecryptable by the smartphone 270 and another subset of encryptedcontrol words would be decryptable by the STB/TV 280. It naturallyfollows that a subset of encrypted media content would be decryptable bythe smartphone 270 and another subset of encrypted media content wouldbe decryptable by the STB/TV 280. Accordingly, the smartphone-based CAsystem 200B disclosed herein in accordance with embodiments spreads themedia content protection over two devices (e.g., the smartphone 270 andthe STB/TV 280). Relative to the reliance of a single STB/TV as asecurity anchor in previously existing CA systems, the multi-pointprotection in the smartphone-based CA system described herein avoids thesingle point of failure in previously existing CA systems.

It should be noted that components are represented in the exemplary CAsystems 200A and 200B for illustrative purposes. Other configurationscan be used and/or included in the exemplary CA systems 200A and 200B.For example, in addition to storing the security profiles in the storage222, entitlements and/or other subscriber data can be stored in thestorage 222 as well. In other words, components can be divided,combined, and/or re-configured to perform the functions describedherein. Further, although not shown in FIGS. 2A and 2B, the exemplary CAsystems 200A and 200B can include other components and/or subcomponentsto facilitate the secure key and content distribution. For example, thedevice key generator 230 can include one or more transmitters totransmit the device keys to the smartphone 270 and/or the STB/TV 280.

The various features of implementations described herein with referenceto FIGS. 2A and 2B may be embodied in a wide variety of forms, and thatany specific structure and/or function described herein is merelyillustrative. In particular, although the CA systems 200A and 200Binclude the smartphone 270, those of ordinary skill in the art willappreciate that various other types of end-user devices, including butnot limited to tablets, wearable devices, computers, and/or portablemultifunction devices, can be used in place of the smartphone 270 inorder to facilitate the security enhancement described herein.

FIG. 3 is a block diagram illustrating media content decryption in anexemplary smartphone-based CA system 300 in accordance with someembodiments. In some embodiments, the smartphone-based CA system 300includes a first receiving device, e.g., a smartphone 310, and a secondreceiving device, e.g., an STB/TV 320. Although FIG. 3 illustrates theSTB/TV 320 as the receiving device for receiving the encrypted mediacontent from the headend (not shown), one or more of the smartphone 310and the STB/TV 320 are capable of receiving and decrypting packets. Assuch, in some embodiments, the smartphone 310 can be the receivingdevice for receiving the encrypted media content from the headend.

As explained above with reference to FIGS. 2A and 2B, the smartphone 310can include the transceiver(s) 274 (FIGS. 2A and 2B) for receivingpackets from the headend 210 (FIGS. 2A and 2B). Further, the smartphone310 can include the controller 272 (FIGS. 2A and 2B) to facilitate thedecryption. In some embodiments, as shown in FIG. 3, the smartphone 310includes a descrambler 312 to decrypt media content packets, an ECMdecoder 314 to decrypt control words, an EMM decoder 316 for decryptingservice keys as well as deriving entitlements for a subscriber 305, anda storage 318 for storing device keys. In some embodiments, thecontroller 272 shown in FIGS. 2A and 2B performs the function of thedescrambler 312, the ECM decoder 314, and/or the EMM decoder 316. Assuch, in some embodiments, the functions performed by the descrambler312, the ECM decoder 314, and/or the EMM decoder 316 are carried out bythe controller 272 (FIGS. 2A and 2B).

Also as explained above with reference to FIGS. 2A and 2B, the STB/TV320 can include the receiver 288 (FIGS. 2A and 2B) for receiving packetsfrom the headend 210 (FIGS. 2A and 2B). Further, the STB/TV 320 caninclude the controller 282 (FIGS. 2A and 2B) to facilitate thedecryption. In FIG. 3, the STB/TV 320 includes a descrambler 322 fordecrypting media content packets, an ECM decoder 324 for decryptingcontrol words, an EMM decoder 326 for decrypting service keys as well asderiving entitlements for the subscriber 305, and a storage 328 forstoring device keys. As such, in some embodiments, the controller 282shown in FIGS. 2A and 2B performs the functions of the descrambler 322,the ECM decoder 324, and/or the EMM decoder 326.

In some embodiments, the subscriber 305 makes a purchase through thesmartphone 310, e.g., the subscriber 305 chooses a channel C to purchasethrough the application on the smartphone 310. The smartphone 310 sendsthe purchase request to the headend. In some embodiments, following theprocess described above with reference to FIG. 2A, based on the securityprofiles, the headend decides whether the receiving devices (e.g., thesmartphone 310 and/or the STB/TV 320) are secure enough for viewing themedia content, e.g., calculating security rankings for the receivingdevices based on the security profiles for the subscriber 305. Othermethods for analyzing the security features of the receiving devices andfor determining whether the receiving devices are secure enough forviewing the content can be used in place of or supplementing thecalculation of the security rankings.

In the case that the receiving devices are secure enough, e.g., one orboth of the security rankings are above a threshold associated with atype of media content, the subscriber 305 submits payment (e.g., by apayment processing application on the smartphone 310) and theentitlement for the subscriber 305 is recorded at the headend (e.g., inthe subscriber data storage 116 in FIG. 1 and/or the security profile inFIGS. 2A and 2B). In some embodiments, the subscriber 305 submits thepayment and the entitlement for the subscriber 305 is recorded when acombined security ranking of the smartphone 310 and the STB/TV 320 isabove the threshold. Moreover, following the key assignment anddistribution process described above with reference to FIG. 2A, theheadend transmits the device keys and/or service keys to the smartphone310 and/or the STB/TV 320. On the other hand, in the case that one ormore of the receiving devices have weak security capabilities, theheadend would not send the device keys and/or service keys to theinsecure device(s).

For instance, a threshold associated with high value media content suchas 4K content may be higher than a threshold associated with lowerresolution media content. Based on the security profile for thesubscriber 305, including the type of media content the subscriber 305wants to view, the profile of the smartphone 310 and/or the profile ofthe STB/TV 320, the headend determines that the STB/TV 320 and/or thesmartphone 310 are not secure enough to watch high value 4K mediacontent and would not distribute the keys for content viewing. On theother hand, in the case that the subscriber 305 requests to watch lowerresolution media content, based on the entitlement information and theprofiles of the smartphone 310 and the STB/TV 320, the headenddetermines that the STB/TV 320 and/or the smartphone 310 are secureenough to watch such media content and would distribute the keysaccordingly.

In order to view the media content, in some embodiments, the subscriber305 chooses the media content to view, e.g., by selecting a channel toview from a package the subscriber 305 has purchased. Utilizing thepairing between the smartphone 310 and the STB/TV 320 (e.g., through thetransceiver(s) 284 of the STB/TV 280 and the transceiver(s) 274 of thephone 270, FIGS. 2A and 2B), the smartphone 310 generates a request tothe STB/TV 320 and instructs the STB/TV 320 to receive media contentcorresponding to the selected channel from the headend, e.g., using thesmartphone 310 as a remote control to signal the STB/TV 320. In responseto the channel viewing request, in some embodiments, the STB/TV 320tunes to the requested channel and receives from the headend encryptedmedia content packets associated with the channel through a one-waycommunication channel (e.g., via satellite communication).

For every received encrypted media content packet, the STB/TV 320determines whether it is encrypted with a control word that can begenerated. For instance, in the case that SK_(C,E) ¹ that is used fordecrypting the control word CW₁ associated with a first media contentpacket Packet₁ is part of SK_(STB), the STB/TV 320 decrypts Packet₁. Onthe other hand, in the case that SK_(C,E) ², which is used fordecrypting the control word CW₂ associated with a second media contentpacket Packet₂, is part of SK_(PHONE), the STB/TV 320 forwards thepacket (while still encrypted) to the smartphone 310 along with theencrypted control word CW₂, e.g., via a secure communication channelbetween the smartphone 310 and the STB/TV 320.

In particular, on the STB/TV 320 side, to decrypt Packet₁, the EMMdecoder 326 of the STB/TV 320 determines that the EMM decoder 326 hasreceived the encrypted service key SK_(C,E) ^(x) that is part ofSK_(STB) in the EMM messages from the headend. The EMM decoder 326obtains the device key K_(STB) from the storage 328 and applies thedevice key K_(STB) to SK_(C,E) ^(x) to the encrypted service keySK_(C,E) ^(x), e.g., in the EMMs, in order to decrypt SK_(C,E) ^(x). Thedecrypted SK_(C,E) ^(x) is provided to the ECM decoder 324 fordecrypting the encrypted CW₁ received from the headend, e.g., in theECMs. In order to decrypt CW₁, the ECM decoder 324 applies the decryptedSK_(C,E) ^(x) to the encrypted CW₁ to derive the unencrypted CW₁, e.g.,by executing a reverse function of ECW₁=F(CW₁, SK_(C,E) ^(x)). The ECMdecoder 324 then provides the unencrypted CW₁ to the descrambler 322,which uses the unencrypted CW₁ to decrypt Packet₁.

On the smartphone 310 side, the smartphone 310 receives the encryptedPacket₂ forwarded by the STB/TV 320. In response to receiving theencrypted Packet₂, the EMM decoder 316 of the smartphone 310 determineswhether the EMM decoder 316 has received the encrypted service keySK_(C,E) ^(y) that is part of SK_(PHONE) in the EMMs from the headend.In the case that the encrypted service key SK_(C,E) ^(y) that is part ofSK_(PHONE) in the EMMs from the headend, the EMM decoder 316 obtains thedevice key K_(PHONE) from the storage 318 and applies the device keyK_(PHONE) to SK_(C,E) ^(y) to decrypt SK_(C,E) ^(y). The decryptedSK_(C,E) ^(y) is then provided to the ECM decoder 314 and the ECMdecoder 314 applies the decrypted SK_(C,E) ^(y) to the encrypted CW₂from the headend, e.g., in the ECMs, in order to derive the unencryptedCW₂, e.g., by executing a reverse function of ECW₂=F(CW₂, SK_(C,E)^(y)). The ECM decoder 314 then provides the unencrypted CW₂ to thedescrambler 312, which uses the unencrypted CW₂ to decrypt Packet₂. Thesmartphone 310 thus decrypts the encrypted media content packet andsends back the unencrypted Packet₂ to the STB/TV 320 over the securechannel established during the paring with the STB/TV 320.

In some embodiments, for performance consideration, the smartphone 310generates unencrypted service keys which are part of SK_(PHONE) andtransmits the decrypted service keys to the STB/TV 320. In suchembodiments, instead of transmitting the encrypted media content packetsand/or the encrypted control words to the smartphone 310, the STB/TV 320receives the decrypted service keys from the smartphone 310 and uses thedecrypted service keys to decrypt the encrypted media content packetsand/or the encrypted control words. In some embodiments, for security,the decrypted service keys are transmitted over a secure channel betweenthe STB/TV 320 and the smartphone 310. For example, the decryptedservice keys may be locally encrypted prior to transmission.

In some embodiments, to further protect the media content, thesmartphone 310 embeds watermarking in the packets sent back to theSTB/TV 320. In some embodiments, the embedded watermarking includes aunique identity, so that the media content is identifiable, thusproviding deterrence against pirated copies. In such embodiments, thesmartphone 310 to receives the encrypted media content, decrypts it,embeds watermarking, and transmits the decrypted media content back tothe STB/TV 320. As such, the secure CA system 300 utilizes thecommunication capability and/or processing capability of the smartphone310 to enhance security.

Though not shown in FIG. 3, in some embodiments, the STB/TV 320 and thesmartphone 310 include additional subcomponents to facilitate the devicepairing. For example, the STB/TV 320 can include a display (e.g., adisplay of TV and/or a display of an STB) connectable to the controller282 (FIGS. 2A and 2B) and the smartphone 310 can include an imagecapturing device (e.g., a scanner or a camera). When being directed bythe controller 282 (FIGS. 2A and 2B), the display displays an identifierof the STB/TV 320 that is scannable by the smartphone 310, e.g., a QRcode with embedded information of the STB/TV 320. The smartphone 310scans the displayed information and extracts the information tofacilitate the pairing in accordance with some embodiments.

The smartphone-based CA system disclosed herein in accordance withembodiments improves security over previously existing CA systems. Byincluding the smartphone as a building block in the smartphone-based CAsystem, the smartphone-based CA system leverages a more capablereceiving device to protect the media content against various attacksand avoids having a single point of failure as in previously existing CAsystems.

For instance, cloning is preventable, since cloning a smartphone is moredifficult to accomplish than cloning an off-the-shelf STB. In anotherexample, because each service has its own unique entitlements and theencrypted service keys included in the EMMs are specific for a channelin an epoch, the entitlement cannot be reused for another service. Norcan the entitlement be reused for the same service and another epoch. Assuch, the key assignment and distribution mechanism described above withreference to FIG. 2A protects the media content against potential CAservice manipulation and entitlement manipulation. In yet anotherexample, because a subset of packets is decryptable by the smartphone, ahacker would have to distribute the encrypted control words to thesmartphone in order to obtain the decrypted control words for contentdecryption. As such, control word sharing is complicated. Further,because the smartphone is capable of embedding watermarks in thedecrypted media content packets to the STB/TV, content sharing can bedetected. As such, the secure content delivery mechanism described abovewith reference to FIG. 2B protects the media content against potentialkey sharing and content sharing.

In some embodiments, the key and content delivery mechanisms describedherein are dynamic. FIGS. 4A-4D are block diagrams illustrating dynamickey and content delivery in exemplary smartphone-based CA systems400A-400D in accordance with some embodiments. Elements common to thesefigures include common reference numbers, and the differences aredescribed herein for the sake of brevity.

To that end, FIG. 4A is a block diagram 400A illustrating service keyassignment and distribution in an exemplary CA system 400A, where asmartphone 420 used by a subscriber 405 is more secure than an STB/TV 1430-1 (e.g., an off-the-shelf STB) in accordance with some embodiments.In FIG. 4A, the subscriber 405 uses the smartphone 420 to register witha headend 410 (e.g., the headend system 210, FIGS. 2A and 2B). Theheadend 410 receives a profile of the smartphone 420 (e.g., hardwareserial number, model number, configuration, firmware version, softwareinstalled, etc.) and a user profile of the subscriber 405 (e.g., userinformation and/or user entitlement). Once the smartphone 420 is pairedwith the STB/TV 1 430-1, the smartphone 420 obtains a profile of theSTB/TV 1 430-1 and transmits the profile of the STB/TV 1 430-1 to theheadend 410. As explained above with reference to FIGS. 2A and 2B, basedon the profiles, the headend 410 (e.g., the controller 240, FIG. 2)stores a security profile for the subscriber 405, locates two distinctdevice keys, and/or distributes one device key to the smartphone 420,e.g., K_(PHONE), and the other device key to the STB/TV 1 430-1, e.g.,K_(STB1).

In some embodiments, as explained above with reference to FIGS. 2A and2B, upon establishing the security profile for the subscriber 405, e.g.,including the profile of the smartphone 420, the profile of STB/TV 1430-1, and the user profile of the subscriber 405, the headend 410calculates a first security ranking for the smartphone 420 and a secondsecurity ranking for the STB/TV 1 430-1, e.g., calculating therespective security ranking as a function of attributes assigned tosecurity features in hardware, software, and/or firmware of therespective receiving device.

Further, based on the security rankings, the headend 410 determines howmany of the service keys would be distributed and used by the smartphone420 and how many would be distributed and used by the STB/TV 1 430-1.For instance, in the case that the first security ranking is higher thanthe second security ranking, e.g., the smartphone 420 has more hardware,software, and/or firmware capabilities than the STB/TV 1 430-1 toprotect media content from hacking, the headend 410 assigns more servicekeys to the smartphone 420 than the STB/TV 1 430-1.

As shown in FIG. 4A, for instance, the headend 410 obtains three servicekeys, e.g., {SK_(C,E) ¹, SK_(C,E) ², SK_(C,E) ³}. For a specific epoch Eand for every channel C to which the subscriber 405 is entitled, basedon the security rankings, the headend 410 assigns two service keys tothe smartphone 420, e.g., SK_(PHONE)={SK_(C,E) ¹, SK_(C,E) ²} and oneservice key to the STB/TV 1 430-1, e.g., SK_(STB1)=SK_(C,E) ³. Theheadend 410 then encrypts the service key set SK_(PHONE) with the devicekey K_(PHONE) and encrypts the service key SK_(STB1) with the device keyK_(STB1). The encrypted service keys are then securely transmitted tothe respective receiving devices, e.g., transmitting the encryptedSK_(PHONE) set to the smartphone 420 and transmitting the encryptedSK_(STB1) to the STB/TV 1 430-1. The ratio of 2:1 with respect to theservice keys assignment and distribution shown in FIG. 4A is merelyillustrative. Those of ordinary skill in the art will appreciate thatother ratios based on the calculation of the security rankings, which isfurther determined based on the security profile of the subscriber 405,can be determined and/or configured through the headend 410.

FIG. 4B is a block diagram illustrating service key assignment anddistribution in an exemplary CA system 400B, where an STB/TV 2 430-2(e.g., an STB with a secure chip) is approximately as secure as thesmartphone 420 in accordance with some embodiments. In FIG. 4B, thesmartphone 420 is paired with the STB/TV 2 430-2, e.g., throughnear-range communication transceivers such as the transceiver(s) 274 ofthe smartphone 270 and the transceiver(s) 284 of the STB/TV 280 (FIG.2). Once the smartphone 420 is paired with the STB/TV 2 430-2, thesmartphone 420 obtains a profile of the STB/TV 2 430-2 and transmits theprofile of the STB/TV 2 430-2 to the headend 410. Based on the profiles,the headend 410 (e.g., the controller 240, FIG. 2) stores a securityprofile for the subscriber 405, which includes but not limited to theprofile of the smartphone 420, the profile of the STB/TV 2 430-2, and/orthe user profile of the subscriber 405. The headend 410 further locatesand/or distributes one device key to the smartphone 420, e.g.,K_(PHONE), and another device key to the STB/TV 2 430-2, e.g., K_(STB2).

In some embodiments, as explained above with reference to FIGS. 2A and2B, based on the security profile for the subscriber 405, the headend410 calculates a first security ranking for the smartphone 420 and asecond security ranking for the STB/TV 2 430-2, e.g., calculating therespective security ranking as a function of attributes assigned tosecurity features in hardware, software, and/or firmware of therespective receiving device. Further, based on the security rankings,the headend 410 determines how many of the service keys would bedistributed and used by the smartphone 420 and how many would bedistributed and used by the STB/TV 2 430-2. In the case that the firstsecurity ranking is the same or approximately the same as the secondsecurity ranking, e.g., the smartphone 420 has sufficient CPU capacityto perform encryption and decryption and the STB/TV 2 430-2 has asecurity enhanced chip, the headend 410 assigns equal (or approximatelyequal) number of service keys to the smartphone 420 and the STB/TV 2430-2.

For instance, in FIG. 4B, the headend 410 obtains two service keys,e.g., {SK_(C,E) ⁴, SK_(C,E) ⁵}. For a specific epoch E and for everychannel C to which the subscriber 405 is entitled, based on the securityrankings, the headend 410 assigns one service key to the smartphone 420,e.g., SK_(PHONE)=SK_(C,E) ⁴ and one service key to the STB/TV 2 430-2,e.g., SK_(STB2)=SK_(C,E) ⁵. The headend 410 then encrypts the servicekey SK_(PHONE) with the device key K_(PHONE) and encrypts the servicekey SK_(STB2) with the device key K_(STB2). The encrypted service keysare then securely transmitted to the respective receiving devices, e.g.,transmitting the encrypted SK_(PHONE) to the smartphone 420 andtransmitting the encrypted SK_(STB2) to the STB/TV 2 430-2. The ratio of1:1 with respect to the service keys assignment and distribution shownin FIG. 4B is merely illustrative. Those of ordinary skill in the artwill appreciate that other ratios based on the calculation of thesecurity rankings, which is further determined based on the securityprofile of the subscriber 405, can be determined and/or configuredthrough the headend 410.

As shown in FIGS. 4A and 4B, the secure key assignment and distributionmechanism disclosed herein in accordance with embodiments is dynamicBased on the security profiles, the headend adjusts the number of keyand/or content delivered to a receiving device, e.g., periodically or inresponse to requests. If a receiving device is more capable to protectthe media content, the headend would deliver more keys and content tothe more secure receiving device. In some embodiments, in the case thatone receiving device is compromised, the headend can deliver the keysand the content to the uncompromised pairing device as shown in FIG. 4C.

In FIG. 4C, initially, the smartphone 420 was paired with an STB/TV 430.In some embodiments, the headend 410 obtains an indication that theSTB/TV 430 is compromised. For instance, the headend 410 canperiodically obtain the profile of the smartphone 420, the profile ofthe STB/TV 430, and/or the user profile of the subscriber 405. Based onthe analysis of the profiles, e.g., by comparing signatures of thehardware, software, and/or firmware of the smartphone 420 and/or theSTB/TV 430, the headend 410 determines whether any tempering of thereceiving device(s) has occurred. In some embodiments, leveraging itstwo-way communication capability, the smartphone 420 periodicallyobtains the profile of the STB/TV 430 through the pairing and reportsany compromise to the headend 410. In response to obtaining theindication of compromise, the headend 410 ceases transmitting the keys,including but not limited to the service keys, the control words, and/orthe device key, and/or the media content to the STB/TV 430. In someembodiments, the smartphone 420 ceases the communication path betweenthe smartphone 420 and the STB/TV 430, e.g., in response to detectingthe compromise of the STB/TV 430 by the smartphone 420 and/or inresponse to being directed by the headend 410 to cease the pairing withthe STB/TV 430. As such, without the pairing, the compromised STB/TV 430would not be able to send a portion of the encrypted media content tothe smartphone 420 for decryption.

In conjunction with ceasing the transmission of keys and content to theSTB/TV 430, the headend 410 increases the number of keys assigned to thesmartphone 420, encrypts the service keys with the device key assignedto the smartphone 420, and transmits the encrypted service keys to thesmartphone 420. In other words, in the case that one of the receivingdevices is compromised, e.g., the STB/TV 430 as shown in FIG. 4C, the CAsystem described herein in accordance with embodiments encrypts andsends all of the encrypted keys along with the encrypted media contentto the uncompromised device. Without the keys, even if the compromisedreceiving device obtains the encrypted media content, the compromisedreceiving device would not be able to decrypt and derive the mediacontent.

In addition to being able to dynamically adjust the number of keys andthe amount of media content delivered, the secure CA system disclosedherein in accordance with embodiments is flexible. In particular, thepairing information included in the security profile enables theflexibility of one watching entitled media content on differentreceiving devices.

For instance, in FIG. 4A, for high value media content, such as 4Kvideos, the off-the-shelf STB/TV 1 430-1 may not have capable hardware,firmware, and software to adequately protect the 4K videos. As such, inorder to view the high value media content, the subscriber 405 mayswitch to a security enhanced receiving device, e.g., the STB/TV 2 430-2with the secure chip in FIG. 4B. FIG. 4D illustrates receiving deviceswitching in a smartphone-based CA system 400D in accordance with someembodiments.

In FIG. 4D, the smartphone 420 has been disconnected from the STB/TV 1,e.g., when the subscriber 405 with the smartphone 420 moving away fromthe STB/TV 1 430-1 and out of a threshold distance from the STB/TV 1430-1 or by the subscriber 405 disconnecting the connection through theapplication on the smartphone 420. Further, the smartphone 420 is pairedwith the STB/TV 2 430-2, e.g., when the subscriber 405 with thesmartphone 420 moving within a threshold distance from the STB/TV 2430-2 or by the subscriber 405 establishing the connection through theapplication on the smartphone 420. Utilizing the near-rangecommunication transceivers (e.g., the transceiver(s) 274 of thesmartphone 270 and the transceiver(s) 284 of the STB/TV 280, FIGS. 2Aand 2B), a secure near-range communication channel is establishedbetween the smartphone 420 and the STB/TV 2 430-2.

In some embodiments, once the smartphone 420 is paired with the STB/TV 2430-2, the smartphone 420 obtains the profile of the STB/TV 2 430-2 andtransmits the profile of the STB/TV 2 430-2 to the headend 410. Asexplained above with reference to FIG. 4B, based on the profiles, theheadend 410 assigns and distributes keys to the STB/TV 2 430-2. In someembodiments, the headend 410 re-locates and/or re-distributes adifferent device key to the smartphone 420 in response to a profileupdate, e.g., the pairing change. Also as explained above with referenceto FIG. 4A, when the smartphone 420 was paired with the off-the-shelfSTB/TV 1 430-1, the headend 410 delivers more keys and content to thesmartphone 420. When the pairing changes such that the smartphone 420 ispaired with the security enhanced STB/TV 2 430-2, based on the updatedsecurity profile, the headend 410 adjusts the number of keys and contentassigned to the receiving devices accordingly. For instance, prior tothe switching, the headend 410 splits the service keys according to aratio of 2:1 between the smartphone 420 and the STB/TV 1 with thesmartphone 420 being more secure and receiving more service keys. Afterthe switching, with the STB/TV 2 430-2 having the secure chip, theheadend 410 splits the service keys evenly between the smartphone 420and the STB/TV 2 430-2. As such, the CA system disclosed herein allowscontent viewing on different receiving devices with continued security.

FIG. 5 is a flowchart representation of a method 500 for service keyassignment and distribution in a CA system, in accordance with someembodiments. In some embodiments, the method 500 is performed at aheadend (e.g., the headend 210 in FIGS. 2A and 2B and/or the headend 410in FIGS. 4A-4D), which includes a controller (e.g., the controller 240,FIGS. 2A and 2B), at least one non-transitory storage for storingsecurity profiles (e.g., the storage 222 in FIGS. 2A and 2B), a devicekey generator (e.g., the device key generator 230, FIG. 2A), and atransmitter (e.g., the transmitter 250, FIGS. 2A and 2B). Briefly, themethod 500 includes obtaining a security profile including a profile ofa first device, a profile of a second device paired with the firstdevice, and a user profile; locating a first device key for the firstdevice and a second device key for the second device; and regulatinguser access to a channel during an entitlement period, includingdetermining a first security ranking of the first device and a secondsecurity ranking of the second device based on the security profile, andassigning a first subset of service keys to be encrypted with the firstdevice key and a second subset of service keys to be encrypted with thesecond device key based on the first security ranking and the secondsecurity ranking, and transmitting the first subset of service keys tothe first device and the second subset of service keys to the seconddevice.

To that end, as represented by block 510, the method 500 includes thecontroller obtaining a security profile including a profile of a firstdevice, a profile of a second device paired with the first device, and auser profile. In some embodiments, the headend further includes areceiver (e.g., the receiver 220, FIGS. 2A and 2B) to facilitateobtaining the security profile. For instance, the first device can be asmartphone, e.g., the smartphone 270 in FIGS. 2A and 2B, the smartphone310 in FIG. 3, or the smartphone 420 in FIGS. 4A-4D; and the seconddevice can be an STB or a smart TV, e.g., the STB/TV 280 in FIGS. 2A and2B, the STB/TV 320 in FIG. 3, the STB/TV 1 430-1 in FIGS. 4A and 4D, orthe STB/TV 2 430-2 in FIG. 4B. The profile of the smartphone can includehardware and subcomponent model number(s), type(s) and version(s) ofoperating system, application(s) installed, SIM information, deviceidentifier(s), and/or serial number(s), etc. The profile of the STB/TVcan include make and model, type of chip(s), identifier(s), and/orfirmware update(s), etc.

As represented by block 512, in some embodiments, the receiver receives,from the first device the user profile, the profile of the first deviceincluding an identifier of the first device, the profile of the seconddevice including an identifier of the second device, and data exchangedduring pairing of the first device and the second device. The controllerthen establishes the security profile based on the profile of the firstdevice, the profile of the second device, and the user profile. In someembodiments, upon establishing the security profile for the subscriber,the headend stores the security profile in the non-transitory storage.

For example, during registration or account setup, the smartphone sendsthe subscriber's information to the headend. Further, the STB/TV candisplay an identifier of the STB/TV for the smartphone to scan in nearrange. The smartphone scans the identifier of the STB/TV and utilizesthe near-range communication device(s) to pair with the STB/TV. Oncepaired, the smartphone obtains further information about the STB/TVthrough the communication between the smartphone and the STB/TV. In someembodiments, the smartphone sends to the headend the information aboutthe STB/TV, the smartphone, and the subscriber, as well as thecommunication between the smartphone paired with the STB/TV. Suchinformation is then used by the headend (e.g., the controller 240, FIGS.2A and 2B) to establish the security profile for the subscriber andstores the security profile in the storage.

The method 500 continues, as represented by block 520, with the devicekey generator locating a first device key for the first device and asecond device key for the second device. In some embodiments, the firstdevice key and the second device key are transmitted by the transmitterof the headend to the first device and the second device. For example,in FIG. 2A, the device key generator 230 generates the device key forthe STB/TV 280 K_(STB) and the device key for the smartphone 270K_(PHONE). Further, the device key generator 230 transmits (e.g.,through the transmitter(s) 250) K_(STB) to the STB/TV 280 and K_(PHONE)to the smartphone 270. In some embodiments, the headend obtains thefirst device key and the second device key from the first device and thesecond device, e.g., once the first device and the second device arepaired. In some embodiments, the device key generator locates andmanages the first device key and the second device key for encryption atthe headend.

The method 500 continues, as represented by block 530, with thecontroller regulating user access to a channel during an entitlementperiod. In some embodiments, in order to regulate user access, asrepresented by block 540, the headend first determines a first securityranking of the first device and a second security ranking of the seconddevice based on the security profile, as represented by block 540.Further, as represented by block 550, the headend regulates user accessby assigning a first subset of service keys to be encrypted with thefirst device key and a second subset of service keys to be encryptedwith the second device key based on the first security ranking and thesecond security ranking. Additionally, as represented by block 560, theheadend regulates user access by transmitting the first subset ofservice keys to the first device and the second subset of service keysto the second device.

For example, in FIG. 4A, for a channel C in an epoch E, the headend 410obtains three service keys {SK_(C,E) ¹, SK_(C,E) ², SK_(C,E) ³} from aservice key generator (e.g., the service key generator 122, FIG. 1). Forthe epoch E and for the channel C to which the subscriber 405 isentitled, the headend 410 determines the smartphone 420 has a highersecurity ranking than the STB/TV 1 430-1. As such, based on the securityrankings, the headend 410 assigns a subset of the service keys, e.g.,two service keys to the smartphone 420, denoted as SK_(PHONE)={SK_(C,E)¹, SK_(C,E) ²} and another subset of service keys, e.g., one service keyto the STB/TV 1 430-1, denoted as SK_(STB1)=SK_(C,E) ³. The headend 410then encrypts the service key set SK_(PHONE) with the device keyK_(PHONE) and encrypts the service key SK_(STB1) with the device keyK_(STB1). The encrypted service keys are then securely transmitted tothe respective receiving devices, e.g., transmitting the encryptedSK_(PHONE) set to the smartphone 420 and transmitting the encryptedSK_(STB1) to the STB/TV 1 430-1.

In some embodiments, as represented by block 542, determining the firstsecurity ranking of the first device and the second security ranking ofthe second device based on the security profile includes associatingvalues to security features extracted from the profile of the firstdevice and the profile of the second device; and calculating the firstsecurity ranking of the first device and the second security ranking ofthe second device based on a function of the values associated with thesecurity features.

For instance, the headend extracts security features such as theprocessor type and speed, types of encryption and decryption software,storage capacity, etc. In some embodiments, the headend calculates thesecurity rankings by assigning values to the security features, e.g.,assigning 1 to a standard chip or an older version operating system inan off-the-shelf STB, assigning 2 to a secure chip in a securityenhanced STB or a newer version firmware, assigning 3 to a crypto engineon a smartphone, etc. The headend then calculates the security rankingsas a function of the values associated with the security features. Insome embodiments, the values assigned to the security features areconfigurable, e.g., decreasing the value assigned to one type of chipovertime as more capable chips are developed, or decreasing the valueassigned to one version of software in response to discovering securityflaws.

Still referring to FIG. 5, in some embodiments, as represented by block552, assigning the first subset of service keys to be encrypted with thefirst device key and assigning the second subset of service keys to beencrypted with the second device key based on the first and the secondsecurity ranking includes assigning an equal number of service keys inthe first and the second subset of service keys in accordance with adetermination that the first security ranking of the first device isapproximately the same as the second security ranking of the seconddevice. On the other hand, if the first security ranking and the secondsecurity ranking are not approximately the same, the headend wouldassign more service keys to be transmitted to the receiving device withthe higher security ranking.

For instance, if a user has a secure smartphone, the security ranking ofthe smartphone is higher. As a result, the headend sends more servicekeys to the smartphone, e.g., distributing two service keys to thesmartphone 420 and one service key to the off-the-shelf STB/TV 1 430-1as shown in FIG. 4A. In contrast, if an STB has a secure chip, thesecurity ranking of the STB is higher or approximately the same as thesmartphone. As a result, the headend sends more service keys to the STBor evenly splits the number of service keys distributed to thesmartphone and the STB, e.g., distributing one service key to thesmartphone 420 and one service key to the STB/TV 2 430-2 with a securechip as shown in FIG. 4B.

In some embodiments, as represented by block 562, the method 500 furtherincludes: (a) receiving a request from the first device to access thechannel; (b) determining whether or not at least one of the firstdevice, the second device, or a combination of the first device and thesecond device is secure to access the channel based on the securityprofile in response to the request; and (c) performing assigning andtransmitting of the first and the second subset of service keys inaccordance with a determination that at least one of the first device orthe second device is secure to access the channel.

In other words, in some embodiments, in response to a request from thefirst device (e.g., channel purchasing and/or subscribing to a servicepackage), the headend analyzes the security features in the profiles anddetermines a security score for the first device and a security scorefor the second device. If the headend determines that at least one ofthe first or the second device is secure, e.g., the security score forthe first device and/or the security for the second device are above athreshold, the headend assigns and transmits the first subset of servicekeys and/or the second subset of service keys. On the other hand, if thefirst device and/or the second device do not have the capacity toprovide adequate protection of the media content, e.g., when thesubscriber requests high value media content, such as 4K content, theheadend may determine that the subscriber cannot watch the 4K contentusing the respective weak security receiving device and therefore willnot send the corresponding service keys (possibly the respective devicekey) to the respective receiving device.

In some embodiments, as represented by block 570, the method 500 furtherincludes detecting an update to the security profile, including at leastone update to the profile of the first device, the profile of the seconddevice, or the user profile, and adjusting a number of service keysassigned to at least one of the first subset or the second subset ofservice keys based on the update. In other words, a subscriber mayswitch to a different smartphone or a different STB for viewingsubscribed media content. In some embodiments, the headend can detectthe changes, e.g., receiving an update to the pairing information orreceiving a report from the smartphone that the STB has beencompromised. In response to detecting the update, the headenddynamically adjusts the service key assignments accordingly to utilizethe more secure receiving device for content protection.

For instance, as shown in FIG. 4D, once the pairing changes, based onthe updated security profile for the subscriber 405, the headend 410determines the STB/TV 2 430-2 is as secure as the smartphone 420, whichis more secure than the STB/TV 1 430-1. Accordingly, the headend changesthe service key distribution ratio from 2:1 to 1:1 between two receivingdevices. In another example, as shown in FIG. 4C, once the STB/TV 430 iscompromised, the security ranking of the STB/TV 430 decreases. As aresult, the headend 410 sends 100% of the service keys to theuncompromised receiving device.

In some embodiments, as represented by block 580, the method 500 furtherincludes regulating user access to the channel during a next entitlementperiod. In some embodiments, regulating user access to the channelduring the next entitlement period includes: (a) determining whether ornot a user is entitled to the channel during the next entitlement periodbased on the user profile; and (b) in accordance with a determinationthat the user is entitled to the channel, determining a third securityranking of the first device and a fourth security ranking of the seconddevice based on the security profile, and assigning a third subset ofservice keys to be encrypted with the first device key and a fourthsubset of service keys to be encrypted with the second device key basedon the third and the fourth security rankings, and transmitting thethird subset of service keys to the first device and the fourth subsetof service keys to the second device. As such, when it is time to renewthe entitlements (for the next epoch), the headend performs the steps inblock 530 for every subscriber.

In some embodiments, as represented by block 590, the method 500 furtherincludes: (a) encrypting at least one control word with at least one ofthe first subset of service keys or the second subset of service keys;(b) encrypting media content associated with the channel with the atleast one control word; and (c) transmitting the encrypted media contentand the at least one control word to the first device or the seconddevice. For example, as described above with reference to FIG. 2B, oneset of service keys SK_(PHONE) is distributed to the smartphone 270 andthe other set SK_(STB) is distributed to the STB/TV 280. The controller240 uses the service keys to the encrypt the control words, e.g.,calculating ECW_(i)=F(CW_(i), SK_(C,E) ^(j)). Further, for every mediacontent packet, the controller 240 chooses a control word, e.g.,choosing CWj, and encrypts the media content packet with CWj. As such,the media content is transmitted in encrypted form and the smartphone270 is a building block in the smartphone-based CA system.

FIG. 6 is a flowchart representation of a method 600 for secure contentdelivery in a CA system, in accordance with some embodiments. In someembodiments, the method 600 is performed at a headend (e.g., the headend210 in FIGS. 2A and 2B and/or the headend 410 in FIGS. 4A-4D), whichincludes a controller (e.g., the controller 240, FIGS. 2A and 2B), atleast one non-transitory storage for storing security profiles (e.g.,the storage 222 in FIGS. 2A and 2B), a device key generator (e.g., thedevice key generator 230, FIG. 2A), and a transmitter (e.g., thetransmitter 250, FIGS. 2A and 2B). Briefly, the method 600 includesscrambling media content associated with a channel during an entitlementperiod, including encrypting the media content using at least onecontrol word to generate encrypted media content, and selectivelyencrypting the at least one control word with a service key from a firstsubset of service keys assigned to a first device or a second subset ofservice keys assigned to a second device paired with the first device inorder to generate at least one encrypted control word; and transmittingthe at least one crypted control word along with the encrypted mediacontent to at least one of the first device or the second device.

To that end, as represented by block 610, the method 600 begins with thecontroller scrambling media content associated with a channel during anentitlement period. As represented by block 612, in some embodiments,the scrambling includes encrypting the media content using at least onecontrol word to generate encrypted media content. Further, asrepresented by block 614, in some embodiments, the scrambling includesselectively encrypting the at least one control word with a service keyfrom a first subset of service keys assigned to a first device or asecond subset of service keys assigned to a second device paired withthe first device in order to generate at least one encrypted controlword. The method 600 continues, as represented by block 620, with thecontroller instructing the transmitter to transmit the at least onecrypted control word along with the encrypted media content to at leastone of the first device or the second device.

For example, as explained above with reference to FIG. 2B, whenencrypting media content associated with a channel C, for an epoch E,the controller 240 encrypts a control word CWi and calculates theencrypted control word ECWi as a function of CW_(i) and SK_(C,E) ^(j),e.g., ECWi=F(CW_(i), SK_(C,E) ^(j)). Further, for every media contentpacket, the controller 240 chooses a control word, e.g., choosing CWj,and encrypts the media content packet with CWj before instructing thetransmitter 250 to broadcast the encrypted media content packet alongwith the encrypted control word.

In some embodiments, as represented by block 630, the method 600 furtherincludes receiving, from the first device or the second device, a userprofile, a profile of the first device including an identifier of thefirst device, a profile of the second device including an identifier ofthe second device, and data exchanged during pairing of the first deviceand the second device; and establishing a security profile based on theprofile of the first device, the profile of the second device, and theuser profile for storage.

In some embodiments, as represented by block 640, the method 600 furtherincludes generating and delivering a first device key to the firstdevice and a second device key to the second device; encrypting thefirst subset of service keys with the first device key and encryptingthe second subset of service keys with the second device key; andtransmitting the encrypted first subset of service keys to the firstdevice and the encrypted second subset of service keys to the seconddevice.

In some embodiments, as represented by block 650, the method 600 furtherincludes adjusting a number of service keys assigned to at least one ofthe first or the second subsets of service keys based on an update to atleast one of a profile of the first device, a profile of the seconddevice, or a user profile.

In some embodiments, as represented by block 660, the method 600 furtherincludes detecting compromise of the second device; and ceasingtransmitting the at least one encrypted control word and the encryptedmedia content to the second device. For instance, in FIG. 4C, once theheadend 410 obtains an indication that the STB/TV 430 is compromised,the headend 410 ceases transmitting the keys (e.g., the service keys,the control words, and/or the device key) and/or the media content tothe STB/TV 430.

In some embodiments, as represented by block 670, the first subset ofservice keys is assigned to the first device and the second subset ofservice keys is assigned to the second device based on a securityprofile. In some embodiments, the service key assignment is performed bydetermining a first security ranking of the first device and a secondsecurity ranking of the second device based on the security profile; andassigning the first subset of service keys to be encrypted with a firstdevice key associated with the first device and assigning the secondsubset of service keys to be encrypted with a second device keyassociated with the second device based on the first security rankingand the second security ranking. In such embodiments, as represented byblock 672, the method 600 further includes scrambling the media contentassociated with the channel during a next entitlement period. In someembodiments, the content scrambling of the channel during the nextentitlement period includes determining whether or not a user isentitled to the channel based on the security profile; and in accordancewith a determination that the user is entitled to the channel,encrypting the media content using one or more control words to generatethe encrypted media content, and selectively encrypting the one or morecontrol words with another service key from the first subset of servicekeys or the second subset of service keys, wherein a number of servicekeys assigned to the first subset of service keys and the second subsetof service keys is adjusted based on updates to the security profile.

While various aspects of implementations within the scope of theappended claims are described above, it should be apparent that thevarious features of implementations described above may be embodied in awide variety of forms and that any specific structure and/or functiondescribed above is merely illustrative. Based on the present disclosureone skilled in the art should appreciate that an aspect described hereinmay be implemented independently of any other aspects and that two ormore of these aspects may be combined in various ways. For example, anapparatus may be implemented and/or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented and/or such a method may be practiced using otherstructure and/or functionality in addition to or other than one or moreof the aspects set forth herein.

It will also be understood that, although the terms “first,” “second,”etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another. For example, a first device couldbe termed a second device, and, similarly, a second device could betermed a first device, which changing the meaning of the description, solong as all occurrences of the “first device” are renamed consistentlyand all occurrences of the “second device” are renamed consistently. Thefirst device and the second device are both devices, but they are notthe same device.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the claims. Asused in the description of the embodiments and the appended claims, thesingular forms “a”, “an”, and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willalso be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

As used herein, the term “if” may be construed to mean “when” or “upon”or “in response to determining” or “in accordance with a determination”or “in response to detecting”, that a stated condition precedent istrue, depending on the context. Similarly, the phrase “if it isdetermined [that a stated condition precedent is true]” or “if [a statedcondition precedent is true]” or “when [a stated condition precedent istrue]” may be construed to mean “upon determining” or “in response todetermining” or “in accordance with a determination” or “upon detecting”or “in response to detecting” that the stated condition precedent istrue, depending on the context.

The invention claimed is:
 1. A method comprising: distributing a firstsubset of service keys to a first device and distributing a secondsubset of the service keys to a second device paired with the firstdevice, wherein the first subset is different from the second subset andthe first device is associated with a viewing device; scrambling packetsof media content associated with a channel during an entitlement period,including: encrypting a first subset of the packets and a second subsetof the packets using at least one control word for the entitlementperiod to generate a first subset of encrypted media content packets anda second subset of encrypted media content packets respectively,selecting a first service key from the first subset of the service keysand selecting a second service key from the second subset of the servicekeys, and encrypting the at least one control word using the firstservice key to generate a first encrypted control word and using thesecond service key to generate a second encrypted control word; andtransmitting the at least one encrypted control word along with theencrypted media content to at least one of the first device or thesecond device, wherein the transmitting causes the first device toobtain the packets for viewing, including causing the first device todecrypt the first subset of encrypted media content packets using thefirst service key and causing the second device to facilitate decryptionof the second subset of encrypted media content packets using the secondservice key.
 2. The method of claim 1, further comprising: receiving,from the first device or the second device, a user profile, a profile ofthe first device including an identifier of the first device, a profileof the second device including an identifier of the second device, anddata exchanged during pairing of the first device and the second device;and establishing a security profile based on the profile of the firstdevice, the profile of the second device, and the user profile forstorage.
 3. The method of claim 2, further comprising: obtaining acombined security ranking for the first device and the second devicebased on the security profile; and determining whether the combinedsecurity ranking is above a threshold for delivering the media contentto at least one of the first device or the second device.
 4. The methodof claim 1, wherein distributing the first subset of the service keys tothe first device and distributing the second subset of the service keysto the second device paired with the first device includes: generatingand delivering a first device key to the first device and a seconddevice key to the second device; encrypting the first subset of theservice keys with the first device key to generate a first subset ofencrypted service keys and encrypting the second subset of service keyswith the second device key to generate a second subset of encryptedservice keys; and transmitting the first subset of encrypted servicekeys to the first device and the second subset of encrypted service keysto the second device.
 5. The method of claim 1, further comprising:adjusting a number of service keys assigned to at least one of the firstor the second subsets of service keys based on an update to at least oneof a profile of the first device, a profile of the second device, or auser profile.
 6. The method of claim 1, further comprising: detectingcompromise of the second device; and ceasing transmitting one or more ofthe at least one encrypted control word, the encrypted media content,and the second subset of service keys to the second device.
 7. Themethod of claim 1, wherein the first subset of service keys is assignedto the first device and the second subset of service keys is assigned tothe second device during the entitlement period based on a securityprofile, including: determining a first security ranking of the firstdevice and a second security ranking of the second device during theentitlement period based on the security profile; and assigning thefirst subset of service keys to be encrypted with a first device keyassociated with the first device and assigning the second subset ofservice keys to be encrypted with a second device key associated withthe second device based on the first security ranking and the secondsecurity ranking.
 8. The method of claim 7, further comprisingscrambling the media content associated with the channel during a secondentitlement period, including: determining whether or not a user isentitled to the channel during the second entitlement period based onthe security profile; and in accordance with a determination that theuser is entitled to the channel during the second entitlement period,encrypting the media content using one or more control words for thesecond entitlement period to generate the encrypted media content,selecting a third service key from the first subset of the service keysand selecting a fourth service key from the second subset of the servicekeys, and encrypting the one or more control words using the thirdservice key to generate a third encrypted control word and using thefourth service key to generate a fourth encrypted control word.
 9. Themethod of claim 7, wherein distributing the first subset of the servicekeys to the first device and distributing the second subset of theservice keys to the second device paired with the first device includes:determining a ratio of the first subset to the second subset of theservice keys during the entitlement period based on the first securityranking of the first device and the second security ranking of thesecond device; and distributing the first subset of the service keys tothe first device and the second subset of the service keys to the seconddevice in accordance with the ratio.
 10. A headend system comprising: acontroller operable to: instruct a transmitter to distribute a firstsubset of service keys to a first device and distributing a secondsubset of the service keys to a second device paired with the firstdevice, wherein the first subset is different from the second subset,and the first device is associated with a viewing device, scramblepackets of media content associated with a channel during an entitlementperiod by encrypting a first subset of the packets and a second subsetof the packets using at least one control word for the entitlementperiod to generate a first subset of encrypted media content packets anda second subset of encrypted media content packets respectively,selecting a first service key from the first subset of the service keysand selecting a second service key from the second subset of the servicekeys, and encrypting the at least one control word using the firstservice key to generate a first encrypted control word and using thesecond service key to generate a second encrypted control word; and thetransmitter operable to transmit the at least one encrypted control wordalong with the encrypted media content to at least one of the firstdevice or the second device, wherein the transmitting causes the firstdevice to obtain the packets for viewing, including causing the firstdevice to decrypt the first subset of encrypted media content packetsusing the first service key and causing the second device to facilitatedecryption of the second subset of encrypted media content packets usingthe second service key.
 11. The headend system of claim 10, furthercomprising: a receiver to receive from the first device or the seconddevice a user profile, a profile of the first device, a profile of thesecond device, and data exchanged during pairing of the first device andthe second device; and a storage to store a security profile establishedbased on the user profile, the profile of the first device, and theprofile of the second device.
 12. The headend system of claim 10,further comprising a device key generator to assign a first device keyto the first device and a second device key, different from the firstdevice key, to the second device, wherein the transmitter is furtheroperable to transmit the first device key to the first device and thesecond device key to the second device.
 13. The headend system of claim12, wherein distributing the first subset of the service keys to thefirst device and distributing the second subset of the service keys tothe second device paired with the first device includes: encrypting thefirst subset of the service keys with the first device key to generate afirst subset of encrypted service keys and encrypt the second subset ofthe service keys with the second device key to generate a second subsetof encrypted service keys; and instructing the transmitter to transmitthe first subset of encrypted service keys to the first device and thesecond subset of encrypted service keys to the second device.
 14. Theheadend system of claim 10, wherein the controller is further operableto scramble the media content associated with the channel during asecond entitlement period, including: determining whether or not a useris entitled to the channel during the second entitlement period based ona security profile; and in accordance with a determination that the useris entitled to the channel during the second entitlement period,encrypting the media content using one or more control words for thesecond entitlement period to generate the encrypted media content,selecting a third service key from the first subset of the service keysand selecting a fourth service key from the second subset of the servicekeys, and encrypting the one or more control words using the thirdservice key to generate a third encrypted control word and using thefourth service key to generate a fourth encrypted control word.